<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style>
	#div1	{width: 200px; height: 200px; background: red; position: absolute; left: 200px; top: 150px; margin: 50px; }
</style>
<script>
	window.onload = function (){
		var oDiv = document.getElementById('div1');
		oDiv.style.left= 500 + 'px';
		
		alert(oDiv.style.left);
		alert(oDiv.offsetWidth);
	};
</script>
</head>

<body>
		<div id="div1"	onclick='alert(this.offsetLeft);'></div>
</body>
</html>
